Torque and Power of an Automobile engine

When we say about an automobile engine, the two parameters that come to our mind are no doubt, Power and Torque.

What is the significance of each?

Torque
If you go through the topic about traction you will understand that the torque gives the acceleration to the vehicle. The maximum value of torque determines the maximum ‘pulling power’ of the vehicle.

Power
From simple physics relation we know that Power = torque times the angular velocity.

Higher power implies higher torque or higher rpm or both

The angular velocity is the indication of the velocity of the vehicle and higher the angular velocity, higher the speeds you can attain. And if the torque at that rpm is enough to generate force greater than the rolling friction and the wind resistance then the vehicle will further accelerate.

To find the maximum speed of a vehicle
Many believe that vehicle cant accelerate beyond the point of maximum power. And that the vehicle becomes ‘unstable’ and will decelerate itself. I don’t believe…
If that is the case how can you push your vehicle to the red rpm range??

In a straight line motion the maximum velocity is found as below…

MY Explanation…

From the engine torque and power curves, select a particular rpm. Find the corresponding torque.
Now assuming no slippage at clutch or any other point in transmission we can find the velocity of vehicle and the torque available at the wheels.
The torque divided the radius of the tyre is the maximum force we can get, provided it is less than the maximum static friction force that is available(explained in Traction section).

Now if this force is more than the rolling resistance and the wind resistance then the body will accelerate further.

Then take an rpm higher than that and repeat the steps.

If this is lower than the resistance offered, take a lower rpm where we get a higher torque and repeat the steps.